Distribution transformers and other types of electrical devices are often subject to over-current (fault) or over-temperature conditions caused by factors such as electrical shorts across distribution lines, internal electrical shorts, overheating, etc. Over-current and over-temperature conditions can damage or destroy a distribution transformer if adequate protection against such conditions is not provided.
Distribution transformers typically are equipped with circuit breakers that interrupt, or break the current path between the primary winding and an associated voltage source in response to an over-current or over-temperature condition.
Circuit breakers usually include a moving contact and a stationary contact. The moving and stationary contacts are in electrical and mechanical contact during normal operation of the distribution transformer, and form part of the current path between the primary winding and the voltage source. The circuit breaker causes the moving contact to separate from the stationary contact in response to an over-current or over-temperature condition, thereby breaking the current path between the primary winding and the voltage source and protecting the distribution transformer from the over-current or over-temperature condition.
An electric arc forms between the moving and stationary contacts as the moving contact separates and is drawn away from the stationary contact. The arc represents a potential safety hazard, and therefore should be extinguished as quickly as possible. The stationary and moving contacts typically are housed within a chamber of an interrupter assembly of the circuit breaker. The chamber is filled with an insulating fluid, e.g., transformer oil, that helps to extinguish the arc.
The insulating fluid can vaporize in response to the heat generated by the arc. Vaporization of the insulating fluid is not desirable, as vaporized insulating fluid is less effective at extinguishing the arc than non-vaporized insulating fluid.
Circuit breakers that address the problem of arc-induced insulating fluid vaporization have been developed. For example, one particular type of circuit breaker comprises a housing formed from stackable cylinders that each form an individual arc chamber. The arc chambers, upon stacking, are aligned so that the moving contact can be drawn therethrough during separation from the stationary contact.
The use of multiple arc chambers is believed to be more effective at extinguishing the arc than a single chamber. The need to manufacture and stack a plurality of individual cylinders, however, can increase the parts count of the circuit breaker, and can increase the number of steps in the assembly process for the circuit breaker.